Effect of Web-mounted Braking Disc on Sound Radiation Characteristics of a Metro Wheel

The effect of the web-mounted braking disc on the sound radiation characteristics of a Metro wheel is analyzed with the numerical method.In the analysis procedure,the three-dimensional finite element model for the wheel is developed and the frequency responses under different excitations are calculated on the basis of the modal summation method.In the dynamic response calculation,three types of exciting forces are considered: the normal unit force at the nominal rolling circle,horizontal unit force at the wheel flange and vertical equivalent irregularity force depending on the average roughness of the wheel and rail at the nominal rolling circle.Then the velocity boundary conditions for the acoustic model are formed by using the vibrations of the structure,and the sound radiation characteristics are calculated with the acoustic boundary element method.The numerical results indicate that that the sound radiation of the wheel is mainly due to the axial vibration of the wheel web,and the noises induced by the radial vibration of the wheel tread are not prominent,compared with those induced by the axial vibration of the wheel web.Besides,the web-mounted braking disc can act as a web-fitted noise screen which can mitigate the noises radiated from the wheel web.When the wheel negotiates a sharp curve,the noises are induced by the axial vibration which is excited by the contact forces at the wheel flange in the lateral direction.After mounting the discs on the web,this type of noises can be effectively reduced.In the meantime,the web-mounted braking discs can also reduce the wheel component of rolling noise to some extent.Besides,This type of discs has a significant influence on the sound radiation directivity,especially in the axial direction.